Optical sensors (Fibre Bragg Gratings (FBG)) have been proposed for many sensing applications. For example a tunable laser can be used to read the values on the sensors arranged in serial or parallel combination of sensors.
The measurement source changes the centre wavelength of the bragg reflectors in the fibre sensors. A tunable laser can be used to sweep across all wavelengths and to find the peak of the wavelength signal for each sensor. These wavelength peak movements are in proportion to the measurement source. The measurement of changes on the FBG sensors is referred to as an interrogator system.
One problem of an interrogator system is that the laser must sweep over a broad range. This broad range slows down the effective measurement speed because the actual data may only be contained in less than 10% of the wavelength spectrum measured. One such interrogator system is disclosed in U.S. Pat. No. 7,649,917, assigned to Intune Networks Limted, provides a tunable laser that scans across all segments in a continuous fashion before determining the sensor wavelengths of interest. The interrogator must sweep over the entire wavelength range which causes in-efficient use of the sweep band/speed as the actual data may only be contained in less than 10% of the wavelength spectrum measured.
Other reported interrogators and tunable laser swept sources also suffer from similar problems, as disclosed in US2011/249973 A1, assigned to University of Maribor, and a conference paper in IEEE LEOS annual meeting 2008, pages 137-148, XP031366144, ISBN: 978-1-4244-1931-9 entitled ‘Generation of high speed, linear wavelength sweeps using sampled grating distributed bragg reflector lasers’ Shane O'Conner et al.
There is therefore a need to provide an improved dynamically swept tunable laser interrogator system and method.